The time it takes for this process to occur in a test tube is measured in the aPPT and PT tests. An early step in this process is the conversion of prekallikrein to kallikrein. The drug warfarin inhibits it by inhibiting reduction of Vitamin K, thus 
The time it takes for this process to occur in a test tube is measured in the aPPT and PT tests. An early step in this process is the conversion of prekallikrein to kallikrein. The drug warfarin inhibits it by inhibiting reduction of Vitamin K, thus preventing synthesis of namesake factors such as prothrombin. One disorder of this process, von Willebrand disease, results from an inability to aggregate (*) platelets. For 10 points, name this process necessary to stop the loss of blood from an injured vessel, which is impaired in hemophilia.
The time it takes for this process to occur in a test tube is measured in the aPPT and PT tests.
blood {clotting} [or {coagulation}]